A great number of pesticidal preparations have been proposed, and a proper preparation is selected therefrom for practical use in accordance with the insect to be controlled. In particular, preparations containing a vaporizing pesticidal component, i.e., those having a high vapor pressure at normal temperature have been used for flying insects such as mosquitos. The problem in using vaporizing components is that the preparations tends to vaporize and lessen its effect before use, for example, during storage. In order to prevent a preparation from vaporizing during storage and to let the preparation be released in a necessary concentration upon use, insect pest control has been carried out frequently by vaporizing a preparation under heating conditions. The pesticidal components contained in this type of preparations which are used under heating conditions usually have a vapor pressure of 1.times.10.sup.-3 mmHg or lower at 30.degree. C.
As an example of insect pest control by vaporizing a preparation under heating conditions, it is cited that a mosquito coil is a spiral coil molded from a kneaded mixture of a preparation and a slow-burning support, which is lit up and burnt whereby the preparation is vaporized by the heat. Pesticidal components useful for mosquito coils include pyrethrin, allethrin, and empenthrin. A mat type or liquid type electric mosquito control apparatus comprises an appropriate support impregnated with a preparation containing a pesticidal component, a part of the impregnated support of which is heated with a heater and the like to release the preparation. Pesticidal components useful for these types include allethrin, furamethrin, and prallethrin. Pesticidal components used in preparations for fumigation or evaporation which release a preparation in a short time period by heating with a heat source, such as heat of combustion or chemical reaction, include methoxadiazone, permethrin, and dichlorvos (Kateiyo Sacchuzai Gairon, Japan Sacchuzai Kogyokai (1991)).
Methods for forcibly vaporizing a preparation by ventilation are known. To cite an example, JU-A-55-954 (unexamined published Japanese utility model application) discloses a pesticidal apparatus having put therein a sublimating insect repellent, such as naphthalene, which inhales outer air through a hole to make the vaporizing component of the repellent vaporize and discharges air containing the vapor through a venting hole. Furthermore, a method for killing insects in which a diffusing material retaining a normal temperature vaporizing preparation, which is shaped into, e.g., a fan, is driven by a driving means to diffuse the vaporizing preparation is also known. This method, although regarded as one method for vaporizing a preparation under non-heating conditions, is considered to be effective when applied to preparations having relatively high vaporizability.
In the above-cited example of the method for vaporizing a preparation by ventilation, it is described that the air to be blown should be hot air when a pesticidal preparation whose vapor pressure ranges from 1.times.10.sup.-3 mmHg to 1.times.10.sup.-6 mmHg at 30.degree. C. is used.
Spraying with aerosol is the only known means for diffusing a pesticidal component having a vapor pressure of 1.times.10.sup.-3 mmHg to 1.times.10.sup.-6 mmHg at 30.degree. C. in space under non-heating conditions for insect control.
For control of flying insect pests, insecticides having high insecticidal activity and a very high vapor pressure, such as DDVP having a vapor pressure of 1.times.10.sup.-2 mmHg at 30.degree. C., have been put to practical use in the form of a vaporizing preparation comprising a resin matrix because of simplicity of use and also because there is no danger of increasing the surrounding temperature or causing burns.
However, DDPV is an organophosphorus compound, the safety of which is a concern. Therefore, vaporizing preparations of other chemicals have been sought for. When an insecticide other than organophosphorus compounds, for example, empenthrin is formulated into a vaporizing preparation, the preparation is effective only in a confined system. It has been used in practice only in deserted places, such as a septic tank, and places closed for a long time, such as a wardrobe and a chest of drawers.
As stated above, most of the insecticidal preparations used against insect pests, especially flying insects, are usually of the type that the active ingredient thereof is vaporized and diffused under heating conditions. This type of preparations require much energy and entertain a danger of increasing the temperature of the equipment or the surrounding temperature and a burn.
Where an active ingredient of an insecticidal preparation is to be vaporized at normal temperature without any heating means, the active ingredient to be used must have a high vapor pressure at normal temperature so as to be supplied to the space in a sufficient concentration. DDVP and the like which have a high vapor pressure at normal temperature have a safety problem. Thus, there has been no effective means available as yet in which a preparation used is safe and hard to vaporize at normal temperature, that is, does not decrease before use but, in use, can be supplied to the surrounding space in a sufficient concentration under non-heating conditions.
Hence it has been keenly demanded to develop a means for controlling insect pests which eliminates the above-mentioned problems by vaporizing and diffusing a highly safe active ingredient under non-heating conditions.